--> Abstract: Accommodation Model for Wolfcamp (Permian) Redbeds at the Updip Margin of North America’s Largest Onshore Gas Field, by Martin K. Dubois and Robert H. Goldstein; #90039 (2005)

Datapages, Inc.Print this page

Accommodation Model for Wolfcamp (Permian) Redbeds at the Updip Margin of North America’s Largest Onshore Gas Field

Martin K. Dubois1 and Robert H. Goldstein2
1 Kansas Geological Survey, University of Kansas, Lawrence, KS
2 University of Kansas, Lawrence, KS

Red siltstones and paleosols are the lateral seal of the mid-continent U.S. Hugoton and Panoma Fields. They dominate the western updip margin of stacked, gas-productive, marine-nonmarine sedimentary cycles (Lower Wolfcamp). Principal flow units are shoaling-upward carbonates deposited during high sea level on a low-relief shelf (Hugoton Embayment of Anadarko Basin). Carbonate units thin to the northwest (factor of four) and are interbedded with reciprocally thicker continental red siltstones that thin oppositely across the shelf (also by a factor of four). Climate changes (arid-humid and prevailing wind direction) and sea-level fluctuation associated with glacial-interglacial cycles, shelf geometry, and proximity to silt source (Ancestral Rockies) are intricately related in an accommodation model for siliciclastic-carbonate cyclic sedimentation on the low-relief shelf.

Large-scale patterns in a 3D subsurface model and sedimentary structures in core support two accommodation mechanisms for thick siltstones. Dominant siltstone facies are mottled and massively bedded (to 3 meters). Layering, either absent or very faint, vertical root traces (to 20 cm long) and well developed Bk paleosol horizons (caliche) suggest an eolian origin for these siltstones (loessites) where silt was trapped and stabilized by vegetation well above a water table during low sea level. Less widespread, but still important, is silt that was trapped at the top of the capillary fringe of a rising water table tied to rising sea level. This mechanism is indicated by adhesion structures in close association with sabkha sedimentary structures. Positive relief on loessites may have reduced accommodation for marine carbonates at the updip field margin.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005